Luminescent tube



Oct. 6, 1936. 1.. T. JONES 2,056,464

LUMINESCENT TUBE Filed Jan. 2, 1929 ATTORNEYS.

A. C. CURRENT SUPPLY.

INVENTOR.

7 JONfS'.

Patented Cat. 16, 1936 UNITED STATES PATENT OFFICE Claims.

This invention relates to luminescent tubes, and especially to a method of producing striations therein.

It has long been known in experimental physics that under certain conditions the positive column of a gaseous discharge tube becomes striated, and this phenomenon is generally designated as striation. It is also known that the number and distance apart of the striae is a function of the pressure of the gas and the diameter of the tube. Keyes, Compton and others have investigated the phenomenon of striations in a mixture of gases, and have shown that in a mixture of helium and hydrogen very few electrons have sufiicient velocity to ionize helium though a great many have sufficient velocity to ionize the hydrogen.

The effect of the relative quantities of the two gases present on the intensity of the spectral 0 lines observed has not been studied. I have been able to demonstrate that by controlling the relative pressures of the gases in the tube as well as the total pressure the coloration of the striae, and indeed even the coloration of the usual apparently continuous discharge may be varied between such wide limits as red and white; this efiect occurring when using a mixture of neon, helium and carbon dioxide. I have also discovered that the striae are aifected by the temperature of the tube and the resulting temperature of the contained gas, and further that it is possible to control the discharge of a tube so that the appearance of the striations produced may be caused to vary over a wide range, and that 0 this can be definitely and repeatedly accomlished by altering one or more of the fundamentals, such as gas pressure, temperature, current density etc.

For the purpose of clearly describing the invention, reference is made to the accompanying drawing, which is a diagrammatic view of a luminescent tube, together with the control apparatus employed.

By referring to the drawing it will be noted that the luminescent tube indicated at 2 is provicled with suitable electrodes 3, and that a side tube is provided as indicated at 4, this tube being partially filled with an absorbent material, such as charcoal or the like, indicated at 5. .The tube 2 is connected with the secondary of a transformer in the usual manner as indicated at 6, while the primary of the transformer is connected as at i with a source of A. C. current supplyas the wires 8 and 9. In order that the current density passing through the tube may be regulated one or more resistances are placed in the wire 9, as shown at I0, II and I2. These represent different values. For instance, the one indicated at 10-l0 ohms, the second, indicated at 11-25 ohms, the third, indicated at 12-50 ohms. Each resistance is provided with a switch such as shown at M, and opening and closing of the switches is accomplished by means of cam members, such as shown at I5, l6 and I1, the cams being mounted on a shaft [8 which is continuously rotated through a reduction gear drive l9 and an electric motor 20. It will also be noted that the side tube 4 is surrounded by a heating coil 2|, and that the circuit therethrough is controlled by a switch 22 which in turn is actuated by a cam disc 23, secured on the shaft l8. In actual operation, when filling the tube, it i first necessary to thoroughly evacuate the same and both the tube and charcoal are out-gassed by heating. Carbon dioxide is then admitted at a pressure of several centimeters and the whole permitted to cool to room temperature, a portion of the carbon dioxide being thus absorbed by the charcoal. The tube is again exhausted,

but at room temperature, or approximately so,

or in other words, below the temperature at which carbon dioxide is copiously emitted by the charcoal. This assures that the charcoal will not later release carbon dioxide, by reason of a reduced partial pressure. If desired carbon dioxide may now be admitted in slight quantities, sufiicient to produce striations. A small quantity of neon is then added and in some instances a small quantity of helium.

When the tube is in operation it will be found, under certain conditions, that striations will lose their whiteness which was due to the carbon dioxide and will be colored with a mixture of the characteristic colors of carbon dioxide, helium and neon, the helium existing as an impurity in the neon, although usually I admit additional helium. The striations are not of uniform color as the mixture of the three components, but instead parts of the striae are variously and beautifully colored. In some portions some colors predominate,.while in other portions an entirely different color may prevail. Under other conditions, a very characteristic appearance that is apparently newin the phenomena of discharge through gases frequentlyv makes its appearance. The discharge is striated longitudinally, several distinct luminous paths extending down the tube. These longitudinal striations seldom coalesce except at their ends, and usually rotate about the axis of the tube, the rate of rotation being a function of beautiful hues.

of the current density. Under these conditions, the application of heat to the tube will cause the discharge to break up into transverse striations It is evident that this means of control of the changes in the striae may be utilized to attract public attention.

When the charcoal has reabsorbed apparently all of the carbon dioxide (if no excess was left in the tube) the appearance of the discharge may be that characteristic of neon and helium, and may appear ,continuous. Raising the temperature of the charcoal by passing a current through the coil 2| will cause liberation of the carbon dioxide and will cause the uniform discharge to change from a reddish color to white. When the current through the coil is shut off, the tube 4 will gradually cool, the charcoal will again reabsorb the carbon dioxide and during this period the longitudinal and transverse striations will appear.

In order to repeat'the cycle of phenomena it is evident that it is only necessary to provide for the cyclic change of pressure, temperature and current density, this being accomplished by increasing or decreasing the current density by cutting in or out the resistances shown at III, II and I2, as this will increase or decrease the current density and similarly the temperature of the gases, and gas pressure is changed by operating the switch 22 as it intermittently opens or closes the circuit through the heating coil 2|.

The particular phenomena or difierent types of striations described have been observed in a particular tube but it is understood that the sequence of events and the magnitude of the changes may be altered to suit the behavior of any particular tube. The most suitable current density is infiuenced to some extent by the thickness and diameter of the tube, and by other conditions that may effect its temperature. The current density is usually varied between such limits as will alter but not destroy the unique appearance of the tube. Hence, the current density itself effects the appearance of the tube, particularly the rate of movement of the striae. I employ means for automatically varying the current density, for instance the resistances indicated at In, H and I2. The charcoal bulb is, in this instance, heated by an internal heating coil through which a current is sent, but it might be stated that I have also employed a gas flame, the heat capacity of the charcoal tube being an effective item in governing the rate of absorption of the gas, and thus the rate of change of the appearance of the tube.

It should be evident that charcoal is not the only gas absorbing material, and also that it may be placed within the tube proper, or in an extension thereof, as here disclosed.

The relative proportions of the gases in the tubes cannot be set forth exactly, since it is exceedingly desirable to make tubes which will vary widely in appearance. It is perhaps most desirable that no two tubes shall have exactly the same appearance, nor vary exactly alike.

While certain features of the present invention are more or less specifically described, I wish it understood that various changes may be resorted to within the scope of the appended claims, similarly that the materials 'and finishes of the several parts employed may be such as the menufacturer may decide, or varying conditions or uses may demand.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. In a device of the character described a tube containing rarefied gas, means for passing an electric current through the gas, a gas absorbing medium in the tube, and means for intermittently heating said'medium to cause it to intermittently expel and absorb gas and thereby vary the gas pressure within the tube.

2. In a device of the character described a tube containing rarefied gases, means for passing an electric current through the gas, a gas absorbing medium in the tube, means for intermittently heating said medium to cause-it to intermittently expel and absorb gas and thereby vary the gas pressure within the tube, and means for intermittently varying the density of the current passing through the tube.

3. In a device of the character described a tube containing rarefied gases, a pair of electrodes in the tube connected with a high tension electric current circuit, a variable resistance to vary the current in said circuit, means for actuating the variable resistance to vary the current density through the tube, a gas absorbing medium in the tube, and means for intermittently heating said medium to cause it to intermittently expel and absorb gas and thereby vary the gas pressure within the tube.

4. In a device of the character described, a tube containing rarefied gases, means for passing an electric current through the tube, means for introducing and removing a gas to vary the gas pressure in the tube during the passage of the current, and means for varying the temperature of the gas.

5. In a device of the character described, a tube containing rarefied gases, means for passing an electric current through the tube, means for introducing and removing a gas to vary the gas pressure in the tube during the passage of the current, and means for varying the density of the current passing through the tube.

LLoYb T. JONES. 

